Generally, a resolver is a kind of sensor for measuring a rotation angle and a rotation speed of a rotating device such as a motor. Recently, the resolver is widely used in various technical fields, particularly to a high-precision control system such as an electric power steering system which demands measurement and control of a rotation angle and a rotation speed with high precision. Therefore, it is needed to accurately figure out and analyze various factors giving an influence on the measurement performance of the resolver and reflect these factors on the design of the resolver in order to minimize a measurement error of the resolver and improve the measurement precision to the maximum.
However, in existing techniques, it is just intended to improve the measurement performance by changing configurations of an excitation coil and an output coil disposed at a stator of a resolver as disclosed in Japanese Unexamined Patent Publication No. 1996-178611, or it is just intended to improve the measurement performance by changing a shape of a rotor of a resolver as disclosed in Japanese Unexamined Patent Publication No. 2005-49183, so an assembly error between the stator and the rotor, which is generated commonly when assembling a resolver, is not considered as a factor giving an influence on the measurement performance of the resolver. In other words, when a resolver is assembled, if an offset error causing a height difference between the stator and the rotor in a direction of a rotary shaft or a twist angle error causing the rotary shaft of the rotor to be inclined with respect to the stator is generated, the magnetic flux flow becomes imbalanced, a leaked magnetic flux increases, and as a result, an input/output voltage transformation ratio and measurement performance of the resolver deteriorate. However, in the existing techniques, this drawback is not reflected on the design of the resolver.
Further, in existing techniques, it is not proposed to optimize a lamination thickness relation between the stator and the rotor and reflect the area relation on the design of the resolver to facilitate the resolver designing work and reduce manufacture costs.